Someone who is so void of personality and sense of humor, that they feel the need to steal the jokes of everyone around them. Upon doing so, they then overuse said jokes until the original joke is no longer even funny. This can lead to frustration/violent outbursts for the original joke creator.

"If I hear that Joke Killer mention the threat of the Zombie Apocalypse one more time, I'm going to destroy her".

"Did you hear the one about the unicorn who walked into a bar? Oh yeah, we all did. Joke Killer's been repeating it 10,000 times a day for the past two months."

1)Someone that ruins a hilarious joke by taking it too far
2)Someone that ruins a moment by telling a terrible joke
3)Someone that laughs really hard at a totally not funny joke

Everyone is having a great time telling jokes and then some guy tells a chicken crosses the road joke that ends with the chicken crossing the road to get to the other side. This person is a joke killer.

The person(s) in a group of friends or co-workers that all too often will end a funny strand of joke so terribly that it will seem intentional. The "killer" should be ridiculed for a large quantity of time after the kill, and to be presented with this definition and a right-handed slap of the face.

Dan "man shes so fat they're gonna have to open both doors to get her in."